1. Field of the Invention
The present invention relates to an optical waveguide having a reflective surface that allows perpendicularly incident light to enter and exit from waveguide cores through which the light propagates, and to an optical module including the optical waveguide. More particularly, the present invention relates to formation of a space in which an optical element to be optically coupled to waveguide cores is mounted, by using a clad opposite the reflective surface.
2. Description of the Related Art
Information transmission has hitherto been performed between boards and between chips in electronic apparatuses by means of electric signals. In order to realize information transmission with a larger capacity at a higher speed, optical interconnection techniques have attracted attention. As one optical interconnection technique, an optical module of a waveguide type using a planar optical waveguide has been proposed.
Japanese Patent No. 3204439 proposes an optical module of such a waveguide type. In this optical module, a projection on which an optical element is to be mounted is formed on a silicon substrate by anisotropic etching, an optical waveguide is formed on the silicon substrate, and the optical element is mounted on the projection of the silicon substrate. This allows an end face of a core of the optical waveguide to be opposed and optically coupled to the optical element.
Since a surface-type optical element can be produced by an easier process than that for an edge-type optical element and is suitable for surface mounting, it is more advantageous than the edge-type optical element from the viewpoint of cost reduction. In particular, a surface emitting semiconductor laser (VCSEL) is capable of high-speed direct modulation, and is extremely promising as a device for a low-cost optical module. Thus, there is a demand for low-cost optical modules using surface-type light-emitting or light-receiving elements.
Japanese Unexamined Patent Application Publication No. 2006-184757 proposes an optical module of a waveguide type to which such a surface-type optical element is applied. In this optical module, a reflective surface inclined 45° is provided at an end of an optical waveguide so that an optical element can be placed on a lower side of the optical waveguide opposite the reflective surface.
In this optical module disclosed in the above publication, the optical waveguide and the optical element are mounted on a silicon platform, and the silicon platform has a recess in which the optical element is mounted. With this structure, the optical element is placed on the lower side of the optical waveguide opposite the reflective surface. The silicon platform on which the optical waveguide and the optical element have been mounted is mounted on a circuit board.